The quantitative study of how fluids (gases and liquids) move.

learn more… | top users | synonyms (1)

5
votes
1answer
175 views

Boiling noodles

Last week I did an expermient which goes as follows, I boiled some amount of water, and then put in a small piece from an uncooked thread of noodle, first of all it went right down to the bottom of ...
2
votes
0answers
18 views

Regarding formulation of a multipoint model of fluid dynamics

Suppose I am trying to formulate a multipoint model of fluid dynamics. I have a procedure for doing so the details of which is not important to this question, but only that it is based on a series ...
1
vote
3answers
96 views

Can a very thin sheet of any material float inside a liquid?

When a body is immersed in a liquid,buoyancy is the net force of all the forces acting on it. Now the forces are equivalent to those which will act on the same volume of liquid.Rightly so,but ...
3
votes
1answer
172 views

Torque of a rotating fluid on a weighing scale

I was trying to do an experiment to measure torque (Moment force) of a rotating fluid. I placed a cylindrical vessel of dia-12cm with 1liter of water on a weighing scale and using a spoon I rotated ...
46
votes
12answers
9k views

How long a straw could Superman use?

To suck water through a straw, you create a partial vacuum in your lungs. Water rises through the straw until the pressure in the straw at the water level equals atmospheric pressure. This ...
1
vote
0answers
53 views

Variance and Intermittency in turbulence

In the turbulent transport of a scalar field, $\Phi$, decomposed into mean and fluctuating components, $\Phi=\left<\Phi\right>+\phi^\prime$, the scalar variance is defined as ...
2
votes
1answer
192 views

Velocity field induced by vortex points along ellipse

I'm investigating the velocity field induced by a continuous distribution of 2D vortex points distributed along an ellipse $\{a\cos\theta,b\sin\theta\}$. I'm interested in the field inside the ...
3
votes
3answers
219 views

Why does an ice cube not twirl along when twirling a drink glass?

When you have a drink with an ice cube and twirl the glass, the liquid itself seems to twirl but the ice cube stays roughly in the same place. Why is this?
8
votes
3answers
4k views

What about negative Pressure?

Here is something I see : Let's say the ideal fluid(water here) of density $\rho$ is drawn from a source by a motor and thrown upwards with a velocity $v$. Now we take the power of motor be ...
1
vote
0answers
138 views

Time required to fill a pipe line

This is quite embarrassing to ask, but I haven't done a fluid flow calculation in a very long time and when you don't use it, you lose it! I have a natural gas pipeline that I want to purge of air ...
1
vote
0answers
56 views

Closed pipe/sound resonance sound type sound coming from mineral processing plant

I work near a very large mineral processing plant which does vibrate our building and there is also a sound/feeling very similar to the closed pipe/sound resonance that is achieved when opening a back ...
0
votes
3answers
275 views

Fluid properties

I cannot understand the following sentence, Without flow , however, shearing stresses cannot exist, and compression stress or pressure is the only stress to be considered. (from A Physical ...
1
vote
1answer
3k views

Flow Rate and Orifice Diameter

I have a electrical/electronics background and have limited knowledge of Fluid Mechanics. So, i will try to be as clear as possible. I am currently working with brake fluid in an ABS system and to ...
0
votes
0answers
36 views

Specific Gravity vs. Pore Space in Chromatography Column

Wondering if we can apply molecular specific gravity to elucidate average time required to pass through a column given porespace, distance and viscosity? This would eliminate the need for special ...
1
vote
1answer
258 views

Compressible flow - subsonic to supersonic and the 2nd law of thermodynamics

I'm reading chapter 16 in Fluid Mechanics by Kundu. It is stated (figures 16.16 and 16.17) that in a constant area duct flow with heating or friction, to go from subsonic conditions to supersonic ...
0
votes
1answer
319 views

Why whirlpool causes force towards its center?

Higher velocity implies low pressure. So in whirlpool the velocity of water have to decrease with radius in order to have force towards its center. My question is how is explained whirlpool formation ...
5
votes
3answers
3k views

Does irrotational imply inviscid?

Let us consider a 2D irrotational flow, such that $\nabla\times\boldsymbol u =\boldsymbol 0$. Defining the stream function such that $\boldsymbol u =\nabla\times\psi \boldsymbol n$ where $\boldsymbol ...
0
votes
0answers
49 views

Stagnation point from complex potential

I just wanted to see if I am doing this right. $$\Omega(z) = U(z+\frac{a^2}{z})$$ So to find the stagnation point: $$\Omega'(z) = U(1-\frac{a^2}{z^2})=0$$ Therefore stagnation points occur at: ...
3
votes
1answer
76 views

(Why) is a solid easier to suspend in a thick slurry than in a liquid?

When making cacao (the non-instant type), one usually mixes the powder with a small amount of milk or water before mixing this slurry into the rest of the milk/water. Some manufacturers of slurry ...
2
votes
2answers
685 views

What would be an appropiate shape for a parachute?

I'm trying to design a parachute that minimizes the descent velocity, but I'm not sure what shape I should use. From what I've read, ellipse-shaped parachutes are too aerodynamic and minimize drag, ...
2
votes
1answer
69 views

Velocity from velocity potential

I have this homework question and I get a different answer to the solutions. In Cylindrical polar coordinates $(r,\theta,z)$, the velocity potential of a flow is given by: $$\phi = ...
1
vote
3answers
39k views

Relation between water flow and pressure

Is there any equation that states the relation between pressure and water flow. I.e. Let's say that in 1 hour with 8mca (water collum meters) pressure I obtain 50m3. What if (giving the same ...
7
votes
1answer
106 views

Critical bathymetric profile to maximize surge and minimize breaking?

Reading about storm surge, I found it fascinating that the gradual slope of the Gulf Coast of Florida resulted in a much higher storm surge but much lower energy release in breaking waves. Is there ...
2
votes
1answer
2k views

What is bulk viscosity and how does it affect the flow? [closed]

What is bulk viscosity and how does it affect the flow? Explain the idea of introducing such a term in the Navier-Stokes equation. What are the consequences if not taken into account?
1
vote
0answers
209 views

Projectile motion of the water surface from water discharging from a pipe

I am looking at pipe flow into a pit. How do I calculate the outside water surface path. I understand how to calculate projectile motion from calculus in terms of a velocity, point object and ...
21
votes
1answer
986 views

How can the Moon have such a strong effect on the ocean?

The gravitational acceleration on Earth is approximately $ 10 \mathrm{m}/\mathrm{s}^2 $. Compared to this, the tidal effect of the Moon's gravity gives a local variation in the acceleration of ...
1
vote
1answer
243 views

Shear, viscosity and expansion of universe

What is the meaning of expansion, shear and viscosity in context of universe? How can we conclude a result after getting a numerical value of above terms?
1
vote
2answers
453 views

Finding an equation relating the mass of a blade of a wind turbine to its velocity

I'm writing up my physics coursework and I thought I'd try and find an equation described in the title. This is my attempt: Is it correct?
2
votes
0answers
209 views

How does an atomizer work?

Will someone please explain how a basic pump atomizer works? I have a feeling it has something to do with pressure and the Venturi effect, but I'd really like to know precisely how they work as ...
3
votes
2answers
958 views

Why water is not superfluid?

My question is in the title. I do not really understand why water is not a superfluid. Maybe I make a mistake but the fact that water is not suprfluid comes from the fact that the elementary ...
7
votes
1answer
2k views

What part of the fan blade actually does the noise generation?

I'm trying to identify the sources of noise in spinning fan blades and what causes them. Is the noise only generated by the lead edge of the blade 'cutting through' air? and different parts of it ...
4
votes
2answers
2k views

Shape of Fan Blades

How is the shape of the blades of an air fan determined? Trial and error, or is there a theory behind it? What are they trying to maximize, volume of air dislocated per rotation?
2
votes
2answers
1k views

How to calculate concentration of vapor at the surface of a water drop

I'm reading a paper that examines the evaporation rates of water. In the final formula, it has the following constant: $c_s - c_\infty $ where $c_s$ is the concentration of the vapor at the sphere ...
3
votes
0answers
645 views

What formulae for calculating fluid pressure change involves these parameters? [closed]

Okay... this is a bit desperate... I am reverse engineering an excel program that is used for calculating outputs for a pressure vessel used for industrial process fluid heating. There is a part in ...
3
votes
1answer
394 views

Question about streamline in boundary layers

I was wondering what the streamlines look like in a boundary layer. I found a picture that shows this: I would like to know if this presentation of the streamline is correct. I don't think that it ...
1
vote
2answers
3k views

Flow rate of a syringe

Suppose a syringe (placed horizontally) contains a liquid with the density of water, composed of a barrel and a needle component. The barrel of the syringe has a cross-sectional area of $\alpha~m^2$, ...
0
votes
1answer
1k views

What are the assumptions of the Navier-Stokes equations?

I wanted to model a real life problem using the Navier-Stokes equations and was wondering what the assumptions made by the same are so that I could better relate my entities with a 'fluid' and make or ...
4
votes
2answers
94 views

How does the correlation length of weather emerge?

The question is pretty simple: If I know the weather where I stand, I can estimate the weather 5 meters or 1 km away away pretty well, but I'll have a hard time guessing what the weather is, say, 50 ...
7
votes
1answer
575 views

How to make the bubbles in my soda drink last longer?

I would like to make the bubbles in my soda drink last longer. For example, one good thing to do is to keep the bottle shut when you don't drink. But what else I can do? Should I try to minimize the ...
1
vote
3answers
748 views

What are the coefficients α, β, and κ in this equation for decompression-induced gas bubble growth?

I am reading a text about gas nuclei I encountered the following formula: $$r = \alpha + \beta \left( \frac{T}{P} \right)^\frac{1}{3} + \kappa \left( \frac{T}{P} \right)^\frac{2}{3}$$ $r$ is the ...
0
votes
0answers
89 views

What does “define analytically” mean?

I'm trying to do my homework in physics but here I have found something that I am not understanding. It says: Define analytically the terms that should stationary flow accomplish. I know that ...
0
votes
1answer
224 views

How to calculate the energy required to generate a vortex? [closed]

I am looking for the formula to calculate how much energy it requires to create a vortex. Can anyone assist please?
0
votes
1answer
191 views

Derive conservation law using divergence theorem

Material scientists have discovered a new fluid property called "radost" that is carried along with a fluid as it moves from one place to the next (just like a fluid's mass or momentum). Let ...
8
votes
4answers
5k views

How does a hole's size affect the distance that water will squirt

I took a bucket, drilled 2 different sized holes on the side near the bottom and filled it with water. The stream of water the proceeded from the larger hole traveled further than the stream from the ...
3
votes
2answers
209 views

What explains the effect of water's path falling around a ball/curve?

Disclaimer: I'm not a physicist. If you take an apple or a ball (or a cylinder works too) and put it under a tap such that the water falls down the side (not the centre) of the sphere, you get water ...
14
votes
8answers
2k views

Why there's a whirl when you drain the bathtub?

At first I thought it's because of Coriolis, but then someone told me that at the bathtub scale that's not the predominant force in this phenomenon.
0
votes
0answers
173 views

Waves produced by a mass of water on the calm sea surface

Suppose we have a parallelepiped shaped box full of water on the surface of the sea. Suddenly the box disappears. What is the shape of the waves vs. time caused by the fall of the water contained in ...
3
votes
2answers
620 views

Example of inviscid flow with drag

This was my engineering viva question and I couldn't think of any example, for I am totally convinced that there cannot be drag in a inviscid flow. It also bothers me whether it is possible, a ...
7
votes
1answer
288 views

Why is there a space between the flame and the nozzle on the space shuttle?

Why is there some space between the flame and the nozzle on the space shuttle? (see above picture)
1
vote
0answers
173 views

How to find outflow pressure/force of air through a pipe

I have been trying to find the correct method for determining the outflow force resulting from a certain amount of air being forced into a pipe of a certain dimension. Essentially i'm trying to ...